Many semiconductor devices and integrated circuits are designed to operate over wide temperature ranges. For example, circuits may be specified to perform correctly at all temperatures in a given temperature range. In some applications, this range may be rather large, for example from as low as -50.degree. C. or lower up to 125.degree. C. or possibly even higher.
In semiconductor physics, the mobility is a measure of the ease of carrier motion within a semiconductor structure. A low mobility implies the carriers inside the semiconductor are suffering a relatively large number of motion-impeding collisions. A large mobility, on the other hand, implies the carriers are zipping along with comparative ease. The resistivity of a structure or material is a measure of the material's inherent resistance to current transport. As is known, the resistivity is inversely proportional to the mobility. In other words, as the mobility goes up, the resistivity will go down; and as the mobility goes down, the resistivity will go up.
The mobilities and resistivities of semiconductor structures will depend upon the temperature, doping concentrations and other factors. In very low doped samples, for example, carrier mobilities monotonically decrease as the temperature is increased. For higher sample dopings, however, the temperature dependence becomes increasingly more complex.